I am able to transform basic sums to vector/matrix equations.
But now I have something like:
$$ c_{p,q} = \sum_{n=1}^N \sum_{r=1}^R \sum_{s=1}^S e_n x_{n-q-s,p} \cdot h_{r,s} \cdot g_r \cdot y^*_{n-s,r} \cdot y_{n-s,r} \quad, \qquad p=\{1,\dots,P\}, q=\{1,\dots,Q\} $$
I don't see the forest for the trees!
The result should be a $P\cdot Q$ vector (if it's easier, can be a $P\times Q$ or $Q\times P$ matrix as well).
How do I do stuff like that? Are there general rules/patterns which I could follow?
I started off taking $e_n$ out and creating a matrix A:
$$ \mathbf{c} = \mathbf{A} \mathbf{e} $$
where $\mathbf{A}$ is an $PQ \times N$ matrix. But now I am stuck factorizing matrix $\mathbf{A}$ ....